The present invention relates to gas turbine engines having afterburners and, more particularly, to a removable flameholder for use therein.
The invention herein described was made in the course of or under a contract, or a subcontract thereunder, with the United States Department of the Air Force.
Modern gas turbine engines for fighter aircraft application utilize afterburners (or augmenters) to augment the energy level of the hot gas stream exhausted from the engine nozzle, thus increasing the thrust level. In such augmenters, fuel is injected into a hot gas stream and ignited. Flameholders mounted downstream of the injectors establish a stable flame front or localized combustion zone for the augmenting fuel.
V-shaped sheet metal gutters have been found to be effective as flameholders, the apex of each gutter being oriented in an upstream direction toward the fuel injectors. These flameholders necessarily operate at very high temperatures and are among the shorter life components of a gas turbine engine. Therefore, it is especially desirable that these parts be easily installed and removed without removal of the engine from the aircraft or removal of the augmenter, or exhaust nozzle, from the engine.
Fan engines with mixed flow augmenters are generally equipped with multilobe mixers to comingle the hot core engine exhaust gases with the relatively cooler fan exhaust gases, and the flameholder is mounted within this mixer at its downstream end. Typically, the mixer envelopes the flameholder resulting in very difficult access to the fasteners attaching the flameholder to the remaining fixed nozzle structure; heretofore the fasteners had to be shielded from the extremely hot afterburning gases and were normally located on the back side (upstream side) of the gutter. Assembly and removal of this type of flameholder with twenty or more (for example) such inaccessible fasteners were extremely difficult, time consuming and costly. This method has been used for many years, however, since it was believed that any fastener accessible from inside the gutter would be overheated. Such fasteners located inside the gutters have, in fact, been tried and have melted. A simple means of mounting flameholders in mixed flow augmenters, therefore, is a needed improvement.
In order that high augmenter performance can be achieved, the flameholder diameter is often larger than the exhaust nozzle diameter. This means that the flameholder cannot be removed and replaced through the exhaust nozzle, thus requiring that the engine be removed from the aircraft and the entire augmenter removed in order to replace the flameholders. This is a time-consuming, costly maintenance procedure. Thus, simple means are needed for removing the flameholder through the exhaust nozzle.